1. Field of the Invention
The present invention relates to a field communication system that performs wireless communication with field devices. Also, the present invention relates to a field communication method by which wireless communication with the field devices is performed.
Priority is claimed on Japanese Patent Application No. 2010-058730, filed Mar. 16, 2010, the content of which is incorporated herein by reference.
2. Description of the Related Art
All patents, patent applications, patent publications, scientific articles, and the like, which will hereinafter be cited or identified in the present application, will hereby be incorporated by reference in their entirety in order to describe more fully the state of the art to which the present invention pertains.
When controlling a wireless field device based on the ISA100.11a field wireless standard, a distributed field control system accesses internal parameters of the wireless field device via a gateway based on the ISA100.11a field wireless standard. An interface for accessing the wireless field device is a GSAP (Gateway Service Access Point) prescribed in the ISA100.11a field wireless standard, and is designated to use an IPv6 address as a parameter that specifies the wireless field device. Also, in the ISA100.11a field wireless standard, a system manager, which exists only one in a network of the ISA100.11a field wireless standard, sets an IPv6 address in the field device. The system manager automatically generates different IPv6 addresses for respective field devices, and sets the generated IPv6 addresses in the field devices, respectively. The algorithm that automatically generates the IPv6 addresses depends on the vendor that provides the system manager.
On the other hand, in the field control system, it is common practice to use a tag name of a field device as a parameter that identifies the field device. The tag name of the field device is expressed as a character string, and a user of the system freely determines and allocates a tag name to the field device.
When the field control system accesses a field device by using a GSAP that is defined in the ISA100.11a field wireless standard, a conversion table for converting the tag name of the field device into an IPv6 address is required.
However, in a large-scale system, engineering such as offline engineering of the system is performed in an environment in which the field device is not connected to the system. In this case, in order for an engineer to prepare a conversion table, it is required that the engineer is aware of the algorithm when the system manager, which is used in the field control system, automatically generates the IPv6 address. However, since the algorithm depends on the vendor, in practice, the engineer cannot aware of the algorithm. Accordingly, it is not possible to prepare the conversion table in the offline engineering environment.
Also, when exchange of the field device is performed, whether or not the system manager generates the same IPv6 address value as before the exchange depends on the algorithm of the system manager. When an IPv6 address which is different from the IPv6 address before the exchange is generated, it is required to update the conversion table. That is, when exchanging the field device, the field control system is required to perform re-engineering.